/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 1997-2007 Sun Microsystems, Inc.  Portions Copyrighted 2008 Richard Schilling.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 *
 * Contributor(s): Richard Schilling (coderroadie@gmail.com)
 *
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.mail.imap;

import java.io.*;
import javax.mail.*;
import com.sun.mail.imap.protocol.*;
import com.sun.mail.iap.*;
import com.sun.mail.util.*;

/**
 * This class implements an IMAP data stream.
 * 
 * @author John Mani
 */

public class IMAPInputStream extends InputStream {

    private IMAPMessage msg; // this message
    private String section;  // section-id
    private int pos;	  // track the position within the IMAP datastream
    private int blksize;  // number of bytes to read in each FETCH request
    private int max;	  // the total number of bytes in this section.
    // -1 indicates unknown
    private byte[] buf;   // the buffer obtained from fetchBODY()
    private int bufcount; // The index one greater than the index of the
    // last valid byte in 'buf'
    private int bufpos;   // The current position within 'buf'
    private boolean peek; // peek instead of fetch?
    private ByteArray readbuf; // reuse for each read

    // Allocate this much extra space in the read buffer to allow
    // space for the FETCH response overhead
    private static final int slop = 64;

    /**
     * Create an IMAPInputStream.
     */
    public IMAPInputStream(IMAPMessage msg, String section, int max, boolean peek) {
        this.msg = msg;
        this.section = section;
        this.max = max;
        this.peek = peek;
        pos = 0;
        blksize = msg.getFetchBlockSize();
    }

    /**
     * Do a NOOP to force any untagged EXPUNGE responses
     * and then check if this message is expunged.
     */
    private void forceCheckExpunged() throws MessageRemovedIOException, FolderClosedIOException {
        synchronized (msg.getMessageCacheLock()) {
            try {
                msg.getProtocol().noop();
            } catch (ConnectionException cex) {
                throw new FolderClosedIOException(msg.getFolder(), cex.getMessage());
            } catch (FolderClosedException fex) {
                throw new FolderClosedIOException(fex.getFolder(), fex.getMessage());
            } catch (ProtocolException pex) {
                // ignore it
            }
        }
        if (msg.isExpunged())
            throw new MessageRemovedIOException();
    }

    /**
     * Fetch more data from the server. This method assumes that all
     * data has already been read in, hence bufpos > bufcount.
     */
    private void fill() throws IOException {
        /*
         * If we know the total number of bytes available from this
         * section, let's check if we have consumed that many bytes.
         */
        if (max != -1 && pos >= max) {
            if (pos == 0)
                checkSeen();
            readbuf = null;	// XXX - return to pool?
            return; // the caller of fill() will return -1.
        }

        BODY b = null;
        if (readbuf == null)
            readbuf = new ByteArray(blksize + slop);

        ByteArray ba;
        // Acquire MessageCacheLock, to freeze seqnum.
        synchronized (msg.getMessageCacheLock()) {
            try {
                IMAPProtocol p = msg.getProtocol();

                // Check whether this message is expunged
                if (msg.isExpunged())
                    throw new MessageRemovedIOException("No content for expunged message");

                int seqnum = msg.getSequenceNumber();
                int cnt = blksize;
                if (max != -1 && pos + blksize > max)
                    cnt = max - pos;
                if (peek)
                    b = p.peekBody(seqnum, section, pos, cnt, readbuf);
                else
                    b = p.fetchBody(seqnum, section, pos, cnt, readbuf);
            } catch (ProtocolException pex) {
                forceCheckExpunged();
                throw new IOException(pex.getMessage());
            } catch (FolderClosedException fex) {
                throw new FolderClosedIOException(fex.getFolder(), fex.getMessage());
            }

            if (b == null || ((ba = b.getByteArray()) == null)) {
                forceCheckExpunged();
                throw new IOException("No content");
            }
        }

        // make sure the SEEN flag is set after reading the first chunk
        if (pos == 0)
            checkSeen();

        // setup new values ..
        buf = ba.getBytes();
        bufpos = ba.getStart();
        int n = ba.getCount();    // will be zero, if all data has been
        // consumed from the server.
        bufcount = bufpos + n;
        pos += n;
    }

    /**
     * Reads the next byte of data from this buffered input stream.
     * If no byte is available, the value <code>-1</code> is returned.
     */
    public synchronized int read() throws IOException {
        if (bufpos >= bufcount) {
            fill();
            if (bufpos >= bufcount)
                return -1;	// EOF
        }
        return buf[bufpos++] & 0xff;
    }

    /**
     * Reads up to <code>len</code> bytes of data from this
     * input stream into the given buffer.
     * <p>
     * Returns the total number of bytes read into the buffer, or
     * <code>-1</code> if there is no more data.
     * <p>
     * Note that this method mimics the "weird !" semantics of
     * BufferedInputStream in that the number of bytes actually returned may be
     * less that the requested value. So callers of this routine should be aware
     * of this and must check the return value to insure that they have obtained
     * the requisite number of bytes.
     */
    public synchronized int read(byte b[], int off, int len) throws IOException {

        int avail = bufcount - bufpos;
        if (avail <= 0) {
            fill();
            avail = bufcount - bufpos;
            if (avail <= 0)
                return -1; // EOF
        }
        int cnt = (avail < len) ? avail : len;
        System.arraycopy(buf, bufpos, b, off, cnt);
        bufpos += cnt;
        return cnt;
    }

    /**
     * Reads up to <code>b.length</code> bytes of data from this input
     * stream into an array of bytes.
     * <p>
     * Returns the total number of bytes read into the buffer, or
     * <code>-1</code> is there is no more data.
     * <p>
     * Note that this method mimics the "weird !" semantics of
     * BufferedInputStream in that the number of bytes actually returned may be
     * less that the requested value. So callers of this routine should be aware
     * of this and must check the return value to insure that they have obtained
     * the requisite number of bytes.
     */
    public int read(byte b[]) throws IOException {
        return read(b, 0, b.length);
    }

    /**
     * Returns the number of bytes that can be read from this input
     * stream without blocking.
     */
    public synchronized int available() throws IOException {
        return (bufcount - bufpos);
    }

    /**
     * Normally the SEEN flag will have been set by now, but if not,
     * force it to be set (as long as the folder isn't open read-only
     * and we're not peeking).
     * And of course, if there's no folder (e.g., a nested message)
     * don't do anything.
     */
    private void checkSeen() {
        if (peek)	// if we're peeking, don't set the SEEN flag
            return;
        try {
            Folder f = msg.getFolder();
            if (f != null && f.getMode() != Folder.READ_ONLY && !msg.isSet(Flags.Flag.SEEN))
                msg.setFlag(Flags.Flag.SEEN, true);
        } catch (MessagingException ex) {
            // ignore it
        }
    }
}
